Japanese cruiser Azuma

Azuma (吾妻) (sometimes transliterated (archaically) as Adzuma) was an armored cruiser (Sōkō jun'yōkan) built for the Imperial Japanese Navy (IJN) in the late 1890s. As Japan lacked the industrial capacity to build such warships itself, the ship was built in France. She participated in most of the naval battles of the Russo-Japanese War of 1904–05 and was lightly damaged during the Battle off Ulsan and the Battle of Tsushima. Azuma began the first of five training cruises in 1912 and saw no combat during World War I. She was never formally reclassified as a training ship although she exclusively served in that role from 1921 until she was disarmed and hulked in 1941. Azuma was badly damaged in an American carrier raid in 1945, and subsequently scrapped in 1946.

The 1896 Naval Expansion Plan was made after the First Sino-Japanese War, and included four armored cruisers in addition to four more battleships, all of which had to be ordered from overseas shipyards as Japan lacked the capability to build them itself. Further consideration of the Russian building program caused the IJN to believe that the battleships ordered under the original plan would not be sufficient to counter the Imperial Russian Navy. Budgetary limitations prevented ordering more battleships and the IJN decided to expand the number of more affordable armored cruisers to be ordered from four to six ships, believing that the recent introduction of tougher Krupp cemented armor would allow them to stand in the line of battle. The revised plan is commonly known as the "Six-Six Fleet". The first four ships were built by Armstrong Whitworth in the United Kingdom, but the last two ships were built in Germany and France. To ensure ammunition compatibility, the IJN required their builders to use the same British guns as the other four ships. In general, the IJN provided only a sketch design and specifications that each builder had to comply with; otherwise each builder was free to build the ships as they saw fit. Unlike most of their contemporaries which were designed for commerce raiding or to defend colonies and trade routes, Azuma and her half-sisters were intended as fleet scouts and to be employed in the battleline.

The ship was 137.9 meters (452 ft 5 in) long overall and 131.56 meters (431 ft 8 in) between perpendiculars. She had a beam of 17.74 meters (58 ft 2 in) and had an average draft of 7.18 meters (23 ft 7 in). Azuma displaced 9,278 metric tons (9,131 long tons) at normal load and 9,953 metric tons (9,796 long tons) at deep load. The ship had a metacentric height of 0.85 meters (2 ft 9 in). She had a double bottom and her hull was subdivided into 213 watertight compartments. Her crew consisted of 670 officers and enlisted men.

Azuma had two 4-cylinder triple-expansion steam engines, each driving a single propeller shaft. Steam for the engines was provided by 24 Belleville boilers and the engines were rated at a total of 18,000 indicated horsepower (13,000 kW). The ship had a designed speed of 21 knots (39 km/h; 24 mph). She carried up to 1,200 metric tons (1,200 long tons; 1,300 short tons) of coal and could steam for 7,000 nautical miles (13,000 km; 8,100 mi) at a speed of 10 knots (19 km/h; 12 mph).

The main armament for all of the "Six-Six Fleet" armored cruisers was four Armstrong Whitworth-built 45-caliber eight-inch guns in twin-gun turrets fore and aft of the superstructure. The electrically operated turrets were capable of 130° rotation left and right, and the guns could be elevated to +30° and depressed to −5°. The turret accommodated 65 shells, but could only be reloaded through doors in the turret floor and the ship's deck that allowed the electric winch in the turret to hoist shells up from the shell room deep in the hull. The guns were manually loaded and had a rate of fire about 1.2 rounds per minute. The 203-millimeter gun fired 113.5-kilogram (250 lb) armor-piercing (AP) projectiles at a muzzle velocity of 760 meters per second (2,500 ft/s) to a range of 18,000 meters (20,000 yd).

The secondary armament consisted of a dozen Elswick Ordnance Company "Pattern Z" quick-firing (QF), 40-caliber, 6-inch guns. All but four of these guns were mounted in armored casemates on the main and upper decks, and their mounts on the upper deck were protected by gun shields. Their 45.4-kilogram (100 lb) AP shells were fired at a muzzle velocity of 700 meters per second (2,300 ft/s). Azuma was also equipped with a dozen 40-caliber QF 12-pounder 12-cwt guns and eight QF 2.5-pounder Yamauchi guns as close-range defense against torpedo boats. The former gun fired 76-millimeter (3 in), 5.7-kilogram (12.5 lb) projectiles at a muzzle velocity of 719 meters per second (2,359 ft/s).

Azuma was equipped with five 457 mm (18.0 in) torpedo tubes, one above water in the bow and four submerged tubes, two on each broadside. The Type 30 torpedo had a 100-kilogram (220 lb) warhead and three range/speed settings: 800 meters (870 yd) at 27 knots (50 km/h; 31 mph), 1,000 meters (1,100 yd) at 23.6 knots (43.7 km/h; 27.2 mph) or 3,000 meters (3,300 yd) at 14.2 knots (26.3 km/h; 16.3 mph).

All of the "Six-Six Fleet" armored cruisers used the same armor scheme with some minor differences, one of which was that the four later ships all used Krupp cemented armor. The waterline belt ran the full length of the ship and its thickness varied from 178 millimeters (7.0 in) amidships to 89 millimeters (3.5 in) at the bow and stern. It had a height of 2.13 meters (7 ft 0 in), of which 1.50 meters (4 ft 11 in) was normally underwater. The upper strake of belt armor was 127 millimeters (5.0 in) thick and extended from the upper edge of the waterline belt to the main deck. It extended 61.49 meters (201 ft 9 in) from the forward to the rear barbette. Azuma had only a single transverse 76 mm armored bulkhead that closed off the forward end of the central armored citadel.